Justice League of Earth? They protect more than america, right? Or is there a JLF (Justice League of France) etc? Sacre Bleau!
In current continuity, they’re the Justice League of America, because Black Canary (a founding member) was a little too eager to connect them to the Justice Society of America.
Since Aquaman, sovreign of Atlantis, was a founding member, it was pretty ironic, pretty early on. Once Wonder Woman joined…well.
The ‘America’ got dropped for a time - first, JL, then JLI (International), which was then redivided into JLA and JLE (Europe) based on where they were based - the JLA was out of New York, the JLE out of Paris. Ironically, IIRC most of the foreign heroes were in the American branch, while the European branch was manned almost entirely by American heroes. But it’s been a while since I’ve read that era, so I might be conflating different teams.
Let’s not forget a founding member was from Mars.
Meta-reason : Superhero comics are largely written by and for American audiences.
Though the JLE era did expand on the League’s worldliness. The teams varied a bit - Fire and Ice were international, and on the American team; however, JLE had Tasmanian Devil, Crimson Fox, and that Indian archer gal whose name escapes me.
The premiere international superhero group was the Global Guardians, who bumped heads with the JL a few times.
And which the League poached Fire and Ice (Originally Green Flame and Icemaiden) from.
Obviously, the name comes from the 40’s Justice Society of America. The group was set up to promote the stars of All-American Comics and their corporate cousin, National Comics. National had Superman and Batman, but All-American had nothing so big, so they decided to create All-Star Comics to spotlight superheroes from both companies that didn’t have their own book. The new book was “All-Star Comics.”
Eventually, Gardner F. Fox came up with the idea to create a team-up of all the characters in the book as the JSA. The first issue involved a meeting of all the heros, then separate adventures, then a finale with everyone. It was an extremely popular title.
Of course, it was Justice Society of America because comics were US-centered, and because it was published by All-American comics.
When superheroes were revived in the late 50s, the idea of a team-up group was obvious (since JSA was so popular). They didn’t want to use JSA, probably because the heroes were all different, so the renamed it “Justice League of America.”
Eventually, it started having spinoffs like JLE and JLI.
I read somewhere that they didn’t want to use JSA because “society” sounded stuffy.